Seizures and reproductive function: insights from female rats with epilepsy.

Abstract

OBJECTIVE:

Chronic seizures in women can have adverse effects on reproductive function, such as polycystic ovarian syndrome, but it has been difficult to dissociate the effects of epilepsy from the role of antiepileptic drugs. To distinguish the effects of chronic seizures from medication, we used the laboratory rat, because an epileptic condition can be induced without concomitant anticonvulsant drug treatment.

METHODS:

Adult female rats were administered the chemoconvulsant pilocarpine to initiate status epilepticus, which was decreased in severity by the anticonvulsant diazepam. These rats developed spontaneous seizures in the ensuing weeks, and are therefore termed epileptic. Controls were saline-treated rats, or animals that were injected with pilocarpine but did not develop status epilepticus. Ovarian cyclicity and weight gain were evaluated for 2 to 3 months. Serum hormone levels were assayed from trunk blood, which was collected at the time of death. Paraformaldehyde-fixed ovaries were evaluated quantitatively.

RESULTS:

Rats that had pilocarpine-induced seizures had an increased incidence of acyclicity by the end of the study, even if status epilepticus did not occur. Ovarian cysts and weight gain were significantly greater in epileptic than control rats, whether rats maintained cyclicity or not. Serum testosterone was increased in epileptic rats, but estradiol, progesterone, and prolactin were not.

INTERPRETATIONS:

The results suggest that an epileptic condition in the rat leads to increased body weight, cystic ovaries, and increased testosterone levels. Although caution is required when comparing female rats with women, the data suggest that recurrent seizures have adverse effects, independent of antiepileptic drugs.

Mortality associated with pilocarpine-induced SE is listed as a function of the day of the estrous cycle when pilocarpine was administered. Each animal was injected with pilocarpine in the morning (see Methods). The mortality in each group was defined either as death during SE (white portion of each bar) or within 48 hrs of SE (black portion of each bar). The total mortality is indicated by the top of each bar (sum of mortality during and after SE). There were no statistically significant differences in total mortality in the 4 groups (proestrus, estrus, diestrus 1 or diestrus 2; Fisher’s Exact test 2*4, p = 0.9502), suggesting that mortality was not influenced by the cycle stage when pilocarpine was administered. Only 3 animals were treated with pilocarpine on estrous morning, because previous studies showed that SE rarely occurs in animals treated on estrous morning using the dose in this study (350 mg/kg;).

A. A micrograph demonstrates normal ovarian morphology in a saline control rat that was euthanized on first morning of diestrus, 3 months after treatment with saline. The ovary is dominated by corpora lutea (arrows) and there is no evidence of cystic follicles. Calibration = 500 μm.B. A micrograph of an ovary from a different rat that was treated with pilocarpine but did not experience more than 1 stage 5 seizure. This rat demonstrated regular estrous cycles and was euthanized 2.5 months after pilocarpine treatment, on the morning of diestrus 1. There are normal corpora lutea (arrows) and a cyst (arrowhead).C. A micrograph of an ovary from a rat that had pilocarpine-induced SE and maintained regular estrous cycles for 2.5 months thereafter, the length of the study. There are many cystic follicles (arrowheads), and some have a broken wall (arrowheads at lower right). The ovary exhibits only a few normal corpora lutea (arrows), despite the fact that the animal was euthanized on the first morning of diestrus, when corpora lutea should be abundant.

Ovarian morphology was examined in animals that were administered saline or pilocarpine and were euthanized approximately 2-3 months after treatment. There were significantly more ovarian cysts in animals that had SE, whether they maintained estrous cyclicity throughout the study or not. Animals were similar in age at the time of treatment, and age at the time of death (see text), so age was unlikely to be a factor. In this figure and others, sample sizes are listed over the bar and significance is indicated by the asterisk. Means and statistical comparisons are listed in the text.

In animals that were treated with saline or pilocarpine, the body weight change in g/day was calculated from the time of treatment to the time of death. Animals that experienced SE gained more weight/day than controls, whether they maintained estrous cycles throughout the study or not. Animals that developed persistent estrus were excluded because this condition is accompanied by chronic elevation of estradiol, which has an anorectic effect in the rodent. Mean values and statistics are provided in the text.

Comparison of serum from control rats and rats that were treated with pilocarpine demonstrates elevated testosterone in rats that had pilocarpine-induced SE, whether they maintained estrous cyclicity throughout the study or did not. Animals were euthanized at the same time of day and time of the estrous cycle (diestrus 1 for cyclic rats, 10:00-11:30 a.m.; diestrus for acyclic rats, 10:00-11:30 a.m.). Mean values and statistics are provided in the text.